Bidirectional Reflectance of H2O Cryofilms on Specular and Diffusing Surfaces

Abstract

The bidirectional reflectance of monochromatic visible and near-infrared radiation from H2O cryofilms on polished copper and black epoxy paint surfaces is measured in the plane of incidence for several film thicknesses, zenith incidence angles, and wavelengths. It is observed that the reflectance distributions retain a significant specular peak even for an H2O film thickness of 500 p. For large incidence angles, superspecular maxima occur in the bidirectional reflectance distributions for H2O cryofilms on black paint substrates but not for H2O films on polished copper. The angular displacement of the superspecuiar peaks from the specular direction depends upon the film thickness in a nonmonotonic manner.